highly-magnetized white dwarfs: formation mechanisms and ... · highly-magnetized white dwarfs:...
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Highly-magnetized white dwarfs:Formation mechanisms and implications for PNe.
J. NordhausNSF FellowCenter for Computational Relativity and GravitationRochester Institute of Technology (USA)
~10% of all white dwarfs are highly magnetized (same for neutron stars)
High-field magnetic white dwarfs (HFMWD): BWD ⇠ 106 � 109 G
~10% of all white dwarfs are highly magnetized (same for neutron stars)
High-field magnetic white dwarfs (HFMWD): BWD ⇠ 106 � 109 G
If the formation of HFMWDs is independent of binary evolution...
... then the fraction of HFMWDs in single stars should be the same as in binary systems.
0 20 40 60 80 100
0
5
10
15
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B (MG)
Kepler et al. 2013
SDSS DR7 Sample SDSS identified ~1,200 detached WD + M dwarf binaries
None are HMWDs
(see also Tout 08)
0 20 40 60 80 100
0
5
10
15
20
B (MG)
Kepler et al. 2013
SDSS DR7 Sample SDSS identified ~1,200 detached WD + M dwarf binaries
None are HMWDs
SDSS identified 149 single HFMWDs
Should we have found HFMWDs in binaries?
(see also Tout 08)
0 20 40 60 80 100
0
5
10
15
20
B (MG)
Kepler et al. 2013
SDSS DR7 Sample SDSS identified ~1,200 detached WD + M dwarf binaries
None are HMWDs
SDSS identified 149 single HFMWDs
Should we have found HFMWDs in binaries?
Within 20 pc, 109 WDs: 20% have a main-sequence companion
Probability of obtaining samples this different from the same underlying population is: 5.7⇥ 10�10 6.2�or
(see also Tout 08)
Nordhaus et al. 2011
HFMWD: no detached companion present.
non-magnetic WDs: detached companion present.
Two options:
1. Presence of detached, long-period companions prevents formation of HFMWD.
2. Orbiting companions were present but were destroyed during formation of HFMWD.
Formation of high-field magnetic white dwarfs from common envelopes
Nordhaus et al. 2011 PNAS 108, 8
Sarah Wellons (Harvard)Dave Spiegel (IAS)Brian Metzger (Columbia)Eric Blackman (Rochester)
Collaborators:
4 5 6 8 10 20 30 40 70 100 200 400 600
1
2
3
4
7
10
20
30
40
70
100
Mc (M
Jup)
P (
hr)
(assumes Ebind
= 1046 erg, MWD
= 0.5 Msun
)
a inner
(! CE=1)
a inner
(! CE=0.
25)
Allowed
ashred
Not Allowed("The Gap")
NGM11
Multiple
Inte
rior t
o "The
Gap
"
and K
nown S
yste
ms
0.005 0.01 0.02 0.05 0.1 0.2 0.5
Mc (M
Sun)
4 5 6 8 10 20 30 40 70 100 200 400 600
0.25!0.35
0.35!0.45
0.45!0.55
0.55!0.65
0.65!0.75
0.75!0.85
0.85!0.95
0.95!1.05
1.05!1.15
1.15!1.25
MWD
(MSun
)
Nordhaus & Spiegel MNRAS 2013 432, 500
Nordhaus et al. 2010 MNRAS 408, 631
0.1 AU1 AU
10 AU100 AU
Fates of KnownPlanetary Systems
ai, engulfed
ai, escapes
af, escapes
pi, engulfed
pi, escapes
ai, Jupiter now
af, Jupiter future
Nordhaus & Spiegel 2013
WD
Inflow Outfl
ow
Boundary Layer
Magnetized WD
Nordhaus et al. 2011 PNAS 108,8Nordhaus & Blackman 2006 MNRAS 370, 2004Nordhaus, Blackman & Frank 2007 MNRAS 376, 599
For shaping PNe see Reyes-Ruiz & Lopez 2001
Important Points:
B-field amplification at convective-radiative boundary with downward diffusion not sufficient.
Companion disrupts; hypercritical accretion initially.
Fields amplify in disk, accrete onto WD surface, survive through termination of the AGB phase.
Important Caveats:
How long does the disk survive?
Hydrogen-rich material deposited in He-burning layer could trigger thermonuclear runaway.